1. Field of the Invention
The field of beam scanning for the purpose of gathering information is rapidly advancing. The commercial application and importance of bar-code reading is well known and is now becoming more sophisticated with the introduction of high density two dimensional bar-code. Code 49, Code 1, and PDF 417 are examples of new bar-code standards that contain information in a two dimensional array.
As information densities increase, scanning with high speed scan patterns becomes necessary in order to read them rapidly. In addition to bar-code reading, the ability to read alphanumeric information is also of great commercial value. Other types of encoded information are being devised, and object recognition requiring scanning readout equipment is also of commercial importance.
As sophisticated portable requirements expand the demand for ever smaller high performance hardware increases.
The present invention provides a portable non-contact moving beam scanning device small enough to be comfortably held with the thumb and fingers like a pen, yet able to automatically scan a moving beam across a distant target containing information such as printed bar-code. The invention contains a novel in-line, or "axial," gyrating scan element, which can accept an input light beam at one end and cause it to emerge as a scanned beam at its opposite end, propagating about a neutral axis in the same general forward direction as it had upon entering the element. With this axial scan element, it is possible to construct an in-line arrangement of a light source and the scan device, thereby greatly simplifying and reducing space requirements for the optical layout of a scanner.
The scanning speeds may range from tens of scans per second to thousands of scans per second, at angles of forty degrees or more, and scanning in two dimensions is also possible. In its preferred embodiments, the invention is distinguished from prior art devices in that the beam passes through an oscillating scan element and generally maintains its original direction upon emergence from the element, rather than consuming the additional space needed to ultimately reverse beam direction.
Configured as a pen-sized and pen-shaped device, the invention also may contain an integrated light source (such as a diode laser), a beam focusing means, and a novel non-imaging light collector coupled to an information processing means for extracting information from the reflected light, as well as an inertially activated switch for turning the device on and off to provide a complete scanning system.
The entire system can be designed to fit into a miniature housing, which may be sized and shaped like a pen or wand, making possible the development of a new generation of compact laser scanning implements not previously available. In doing so the present invention overcomes many of the limitations of prior art devices such as contact-wands which must contact the bar code to be read and pistol grip bar code readers which are presently far larger than is desirable.
In particular, the invention relates to an integrated beam scanning module for use within the device, which can be easily fabricated in the form of a cylindrical module having dimensions of about three eighths of an inch in diameter by three quarters of an inch in length. The scan module's rugged housing may be made from a heat dissipating material (such as anodized aluminum) for conducting heat away from a laser diode.
The present invention also provides in a pen or wand size scanning system, the capability of generating two-dimensional scan patterns such as rasters or omnidirectional patterns for reading printed indicia with little regard for orientation of printed material. It also enables one or two dimensional high density bar-code targets to be read at significant distances. This is done by means of high speed wide angle rastering scan patterns.
The present invention further includes methods for using a low mass pen-sized laser beam scanner mounted in ways that are impossible or cumbersome using current state of the art devices. For example, the device can be housed in a pen-sized tube allowing new mounting possibilities such as attachment to a light weight cap or safety helmet, to the temple of eyeglass frames, badges or a robot arm. Mounting several similar devices in a bundle can achieve overlapping scan patterns or redundancy in small spaces.
The invention also relates to methods for using the pen-size scanning system to inexpensively generate raster patterns. This is done by bending one's wrist while holding a device which produces a one-dimensional line scan, thereby deflecting the scanned beam to effect both X and Y-axis scanning, a process which may be termed "wrist rastering".
In addition, the invention also relates to methods for using the pen-size scanning system by visually impaired individuals to avoid obstacles and to read books printed in two dimensional bar-code or conventional print. It also relates to methods of using the scan system by individuals with various other physical disabilities, who are not adequately accommodated by the design and physical operating requirements of existing "pistol-grip" scanners.
2. Description of the Prior Art
The utilization of portable scanning devices for reading bar-codes is experiencing tremendous commercial success. Among the most popular portable bar-code scanners available today are those which fall into the contact wand category and those in the non-contact, pistol shaped category.
The contact wand type bar-code reader device commonly used today is packaged so as to resemble a thick pen, about one half inch in diameter. It is light, rugged and easy to hold, but its use is confined to reading smooth flat surfaces with relatively high quality printed bar-code. These devices typically contain a light emitting diode light source and an electronic photo detector. A small spherical sapphire tip with an extremely short focal length focuses the light at the tip of the wand. Because of this short focal length the device has virtually no depth of field and a major drawback of being essentially limited to contact reading.
The contact wand is used by bringing it into contact with the surface upon which the bar-code is printed and then dragging the tip across it, yielding only one scan per swipe of the user's hang. Because the wand tip devices must first be oriented so that the anticipated motion of the hand will be able to pass through all bars of the code, a significant degree of skill to drag it across the bar-code at a uniform and suitable rate of speed is required for successful operation. Surface damage often results in many repeated reading attempts as well as poor productivity.
Contact-type scan wands are also poorly suited to scanning printed material that has damage (as coupons usually do when carried around in a purse), or when the surface that is labeled or printed upon is curved, soft, irregular or wrinkled such as mailing pouches, or with other generally non-flat surfaces upon which bar-code is printed.
In order to overcome some of the problems associated with contact wand readers, portable laser reading guns were developed. These typically read bar-code at distances ranging from inches to several feet. Consequently, these are more effective for reading bar-codes printed on irregular surfaces, but have the drawback of being far bulkier than contact wands.
One such gun-type device, described in U.S. Pat. No. 4,387,297, is a non-contact portable gun-shaped laser scanner with a pistol grip and a trigger with which to activate the scan sequence. The gun-type scanners have ergonomic characteristics similar to those of a hand gun, yet are generally bulkier; in many cases, they are more like a hand-held hair dryer and are not amenable to being carried in a pocket or to storage in a cash drawer.
A gun reader includes a light source which produces a laser light beam that is directed away from a target. The beam is internally reversed by means of a series of mirrors either fixed or mounted on one or more moving motor shafts causing it to scan, whereupon the beam finally emerges in the direction of the selected target. This arrangement requires ample layout space so the outgoing beam is not occluded by the laser light source and light collection apparatus.
To use this gun-type scanner, it is aimed by sighting the target to be read and then the trigger is squeezed with the user's index finger, whereupon a scanned laser beam emerges, which, if suitably aimed and oriented, will sweep across a bar-coded label and read the information encoded thereon.
The aim and shoot characteristics of the gun-type device are suited for long range bar-code reading on the order of a few feet, but remain clumsy for short range reading jobs where distances of about six inches to one foot are involved, especially when the user is seated at a desk or counter. In such cases, the ergonomic benefits are lost and become liabilities.
Because of its size and handling requirements, numerous problems associated with the pistol-grip aim and shoot design result.
Aim and shoot applications require a significant amount of hand-eye coordination to a) hold, b) aim, c) trigger and d) orient the scanner so the scan line will pass through all bars of the code. With these functional demands placed on the user, difficulty of operation increases significantly with any physiological impairments or severance of digits the operator may have. Placement of the trigger, for instance, assumes that the user has a functional index finger. If fingers further down the hand are the only ones capable of the necessary squeezing movement, the user has no choice but to try to operate the gun by holding it in a way other than the design accommodates. Of course, users with substantial disability impairing their ability to grip at all, are entirely precluded from using aim and shoot type pistol grip devices. Because of its weight, dimensions and triggering mechanics, other methods of holding and moving the device without using the hand and fingers to grip and manipulate are ungainly.
Pistol grip aim and shoot scanners create special problems for users with disabilities, and reasonable accommodation problems for employers under the new Americans with Disabilities Act. Another problem is realized when observing the extent to which an able-bodied user's gripping hand is monopolized by the holding and operation of the gun. For example, a clerk using the device at a checkout counter, in conjunction with a cash register key pad for unlabled items typically uses one hand to pick up and orient items advancing on a conveyor belt so that the label can be read. The other hand is used to operate the scanner gun. It has been observed that whenever the clerk needs to use the keypad, s/he must first lay down the gun to free up the hand, use the keypad, then pick up the gun once more. This can cut into productivity significantly and impede the flow of work.
Another problem associated with aim and shoot devices is that they typically require operators working at counters to pull their using arm back at the elbow so that the end of the gun clears the surface of the label they are attempting to scan. In toy stores, for example, some items or boxes are so bulky that operators of average height must remove the item from the counter, hold it off to the side with one hand, at a lower level than the counter so that the end of the gun can clear the target scanning surface, while attempting to scan with the other hand.
Apart from being unsound from a general human factors viewpoint, this extra movement can create discomfort for people with arthritis, bursitis, and other diseases, injuries or disabilities affecting the articulations of the shoulder. The problem is worsened if the operator needs to be seated at a counter.
In the instance of a person with a disability who must be seated at a work counter designed for a standing able-bodied person, the Americans with Disabilities Act may require that the work area be redesigned as a "reasonable accommodation" if a friendlier scanner design were not available.
The very shape of gun-type scanners can pose safety concerns in some instances, such as an employee working on a late shift in a warehouse carrying and using the gun, wherein contract security personnel might become unduly alarmed by the pistol-like appearance, especially when observed at a distance.
Another type of scanning gun is described in U.S. Pat. No. 4,652,750. In the case of this device, the scanning beam is not automatically placed in motion and the user must not only aim the device from a distance at the target label, but must then continue to manually direct the beam from one side of the label to the other without falling outside the boundaries of the label and maintaining a uniform speed in doing so. This is extremely difficult, since bar-code labels are typically about the size of a large postage stamp. Also, relatively minor curves in the scan line caused by the amplification of normal hand movement as a function of target distance may throw off the time values assigned to each element of the bar code and result in a bad scan. Repeated attempts are more and more likely to be poor as well, as the result of natural hand-arm fatigue and frustration. This device was therefore not very successful commercially.
Another prior art invention describes a moving beam bar-code scanner that is affixed on the back of the operator's hand. The fingers are freed from the arresting level of involvement required to operate a pistol-grip mechanism, yet the design is nonetheless ungainly because the back of the hand is not well-suited to aiming the beam.
Another category of readers for bar-code and printed matter are the so called CCD or "Charge Coupled Devices" types, which use an imaging technique similar to that in facsimile machines. CCDs do not contain lasers or other light beam sources and are much different from the beam scanning readers. CCD readers contain photo diode arrays upon which the bar-code must be imaged. Computer programs then decipher the imaged information pattern thus formed. Generally, CCD readers must be placed on top of and cover the target bar-code, have poor depth of field and are limited as to the size of bar-codes to be read, and thus possess many of the limitations of contact readers. Experimental CCD systems with expensive large lens focusing systems can achieve modest improvements in the depth of field, but are bulkier and expensive.
Some laser scanners utilize polygonal mirrors rotated by motors to generate scan lines by reflecting a laser beam off the mirrors as they pass in front of the beam. Owing to a complex optical path with ample head room requirements for the beam to escape, these scanners are bulky and at best may be packaged in boxes or gun shaped housings, but not smaller.
U.S. Pat. No. 4,871,904 describes a two-dimensional scanning system in which a laser source light beam is directed at a scanning element having a pair of mirrors which reflect and redirect the beam so that it emerges as a scanning beam travelling in the same general direction as the source beam. The mirrors are each mounted at an angle on a motor shaft, and motor rotation provides a scanning beam. Because of the size of the motors required, this system is ill suited to hand-held scanners. It has a limited range of scan patterns, all of which include a significantly curved path of the moving beam; it cannot produce a line or raster scan. Also, because of motor inertia, this system is ill suited to the intermittent operation characteristic of a hand-held scanner.
Existing fixed mount scanners are not amenable to mounting on robot arms for use on production lines because of their size and weight.
Reluctance of employees to accept new bar-code scanning applications because of the clumsiness or inconvenience of the equipment is also an important issue. For example, nurses, in the course of their patient care duties, have been resistant to the idea of using bulky bar code readers because of the clumsiness and inconvenience of the devices. Other problems with prior art devices stem from the inability to mount them in tiny housings because of the space consuming clearance requirements associated with non-axial optical designs.
U.S. Pat. No. 5,198,651 describes a somewhat compact scanning device having a unitary framework structure with numerous ribbed elements to hold its components closely together and to shock mount them. Even so this scan engine is too bulky to fit into a pen-size housing and cannot produce two dimensional scan patterns. It suffers from the common optical layout problem of having to provide ample head room for the emerging scan beam.
None of the known moving beam or CCD scanning systems which can automatically scan one or two dimensions in order to read information is small enough to be packaged into a housing having the general size and shape of a pen or wand.